Power Output Characteristics during a triathlon



ghutchinson

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Dec 2, 2003
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I have a couple of questions regarding power output and pacing during a triathlon, where you have to run 10, 15 or 21km after the bike.

i) Assuming two riders have the same aerodynamic and weight properties, if they both average the same watts (ie. 270w) during a hilly bike in a triathlon, will they essentially have the same time?

ii) What if one rider exerts a greater than avg. effort up the hills and a lower than avg. effort down the hills but still averages 270w while the other rider rides smoothly and holds 270w throughout the ride?

iii) Assuming a varied effort strategy in 'ii' is faster, how much time can be saved by riding at >100% of avg. effort up the hills and <100% down the hills over 40-60km? How significant is this effort and have others found that this strategy works in a triathlon or not? How much extra effort can a rider 'afford' to put out up the hills, if any? Or should they just hold a higher watts smoothly throughout the ride?

Does anyone have any experience in the area of having to run after a time trial (triathlon) and can they please provide input and experiences and hyposthesis? I have searched various place on the internet and I haven't found many discussions on this subject.

I apologize in advance to any roadies who have wasted their time reading a post with the word triathlon in it :)
(Even L.A. used to race in a Speedo :D
 
I'd assume that the two riders in (i) would have similar times but there'd be other factors such as bike handling, what "racing line" had been followed etc etc that can have a significant impact on time.

Personally, I find it beneficial to pace evenly throughout the ride. If there are places on the course that force you to reduce the effort, ie a technical descent, then you still don't want to push yourself too much past your threshold during the uphill section and I'd expect that to be even more important in a triathlon where you still have the run to go afterwards.
I'd also bet that most people don't believe how much they hold back on descents until they see the power numbers displayed. The sensation of speed seems to equate to a feeling of power - until you look down and you're only at 75% of threshold. LOL.
 
What I have been noticing after reviewing friends powertap files is that they have way more power spikes (ie. they are trying to hold 270w but have times where they hit 400w and 350w for 10-20 sec. on many occasions - >20 times) and they end up 3-4 minutes faster than me over 55km but have the same average power.
Some of them can run afterwards and some can't.

A more general Time Trial question - do you get faster times for a hilly time trial if you exert 20-30% more power on the uphills, 20-30% less power down the hills and steady on the flats vs. steady the entire time, both averaging the same power?
 
ghutchinson said:
...A more general Time Trial question - do you get faster times for a hilly time trial if you exert 20-30% more power on the uphills, 20-30% less power down the hills and steady on the flats vs. steady the entire time, both averaging the same power?
Perhaps not 20-30%, but variable pacing for hilly time trials is a bit faster. What it does in terms of your ability to run afterwards is debatable.

Google "variable power time trial pacing" and you'll get hits like this:
http://www.ncbi.nlm.nih.gov/pubmed/11083127

or check out Alex Simmon's blog with his very cool post TT analysis tool that models ideal pacing:
http://alex-cycle.blogspot.com/2009/03/old-skool.html

-Dave
 
ghutchinson said:
What I have been noticing after reviewing friends powertap files is that they have way more power spikes (ie. they are trying to hold 270w but have times where they hit 400w and 350w for 10-20 sec. on many occasions - >20 times) and they end up 3-4 minutes faster than me over 55km but have the same average power.
Some of them can run afterwards and some can't.

A more general Time Trial question - do you get faster times for a hilly time trial if you exert 20-30% more power on the uphills, 20-30% less power down the hills and steady on the flats vs. steady the entire time, both averaging the same power?
How big are these hills? If they're pretty small and only take a minute to get up them then sure, give it an extra 10% or so... but if we're talking 10+ minutes at something over a 5% grade then you might want to stay closer to threshold.

Conversely, make sure that you have a gear big enough to allow you to stay on the tri-bars on the way down the other side. If you can't do 130+rpm while on the tri-bars then you might want to consider a monster gear to enable you to stay aero when you need that advantage the most. If you know there's a 5% hill you'll be going down and there's a strong likelyhood of a tailwind then you'll be a fool to limit yourself to the usual 53x12 top gear - you'll be haemoraging time by the bucket load. You can never gain time in a time trial - you only lose time. The winner is the one that loses the least...

For some oddball reason people think there's something taboo about gearing, like it was once etched in the monoliths of Stonehenge that the Druids proclaimed that ye shalt not use more than 120 of thine imperial inch gears or one shall be sacraficed on the altar stone... If you need 58x11 to stay around 100rpm and keep on the bars and keep the power up where it should be - then that's what you need. The same goes for going uphill too. No prizes for the biggest gear up the hills.
 
ghutchinson said:
i) Assuming two riders have the same aerodynamic and weight properties, if they both average the same watts (ie. 270w) during a hilly bike in a triathlon, will they essentially have the same time?
not sure here that avg wattage is relevant for such an analysis. NP would probably be far better. So the quick answer to your question is probably no.
ghutchinson said:
iii) Assuming a varied effort strategy in 'ii' is faster, how much time can be saved by riding at >100% of avg (...) Or should they just hold a higher watts smoothly throughout the ride?
I would advise that you create an excel spreadsheet so that you could perform your own calculations to figure this out. I remember having done one for myself few years back but I don't remember where I put it. Essentially, it would allow me to perform what-if scenario, just like when business need to budget their stuff using a buch of what-if scenarios.

To create this spreadsheet, I used a website that specializes in performing powerbased calculation given a slop, given an altitude, given any other parameter. This sreadsheet was therefore design to cummulate x number of segments having their caracteristics (slope, cda etc).

A hononorable member by the nick of RapDaddyo once made a significant amount of research on this particular topic. You may want to use the search function of this site to navigate in his posts. Haven't heard from RapD for a while however.

ghutchinson said:
Does anyone have any experience in the area of having to run after a time trial (triathlon) and can they please provide input and experiences and hyposthesis? I have searched various place on the internet and I haven't found many discussions on this subject.
what would you need to know?

Bare in mind that avg power as returned by default by most powermeter in real time isn't sufficient to monitor an overall pacing strategy on hilly paths. Ergomo I believe (if it still exists) use to provide real time NP.
 
For years I have subscribed to the 'keeping your power constant' is the fastest, most efficient way to race time trials and triathlons (using a 55x11 to keep the power up on the downhills). In the last year, more and more of my friends are using power to race with and they don't keep their power anywhere close to as smooth as mine, yet we still average about the same, yet they are a couple of minutes faster than me. The hills are not 'climbs', they are just hills. I don't think there are any 10 minute hills in southern Ontario? Maybe a couple. All under 3 minutes, many are 1-2 minutes and maybe 4-5% grade. I am keeping my power at 270w with very little changes (NP and Avg. power would be almost identical, <5w difference?), they are spiking up to 330-350w and sometimes even spiking up to 450-500w for a couple of seconds. We average the same, but he is 3 minutes faster. His NP would be quite a bit higher because of the power spikes.
The question comes down to, how do you have the lowest combined bike + run time? I could have hit the hills a lot harder but I feel I would be sacrificing my run. My theory is that I may lose 2 minutes on the bike by not increasing my power by 20w on the hills but I gain >2 min. by having fresher legs on the run.
Is there a chance that I wrong in my thesis?
Should I spend more time in my training focusing on hill intervals at 30-40w above my race pace for 2-3 minutes with the purpose of using that power range in races? (I do these already but for the purpose of pushing up my FTP, not to use that intensity in a race).
I appreciate the time you have taken with your responses.
 
That's why recommendation to kind of not pay too much attention to power while riding, you know, the "stay in the zone and be careful not to outdo it" sort of attitude, we got to be careful not to get trapped into this.

Some report finding iso-power tts more difficult, they (I should say we) find that it's little easier to push for a long while then feel a little relief. So if VI > 1.0 can justify itself due to coarse specifics, then you may be killing to birds with one stone.

Try it. I believe the web site was called cyclinganlysis or analyticalcycling or something alike, if you google cycling and analysis and power as keyword, you'll find a site that can perform power to speed conversion and calculate duration given distances and slopes.

You'll see that there are no silver bullet hidden in there, but "few minutes faster than me" is fairly constistant with the calculations I ran for myself, and you named a huge loss of energy, down the slope it takes bigger power in order to make small difference. And up the long steady slopes there are noticeable time savings to be made just by increasing power slightly over avg.

For long distance triathletes I believe it is worthwhile to try keeping an eye on avg power even if it won't be as precise as real time NP. 6hours of cycling can sometimes be little more difficult to pace only on RPE.

Dr. Phil Skiba once (few years back) made some research on a running TSS equivalent. Not sure where he stands at the moment. If there's anything, things should be improving as a result of better technology availability.

If you're a good swimmer, and especially if you use a wet, then time spent to swim doesn't fully count, or at least you should swim in a way to be very fuel efficient. So (to me) that doesn't really count.

** edit ** http://www.analyticcycling.com/ tool kit / static forces on rider should be sufficient for most cases
 
ghutchinson said:
I have a couple of questions regarding power output and pacing during a triathlon, where you have to run 10, 15 or 21km after the bike.

i) Assuming two riders have the same aerodynamic and weight properties, if they both average the same watts (ie. 270w) during a hilly bike in a triathlon, will they essentially have the same time?

ii) What if one rider exerts a greater than avg. effort up the hills and a lower than avg. effort down the hills but still averages 270w while the other rider rides smoothly and holds 270w throughout the ride?

iii) Assuming a varied effort strategy in 'ii' is faster, how much time can be saved by riding at >100% of avg. effort up the hills and <100% down the hills over 40-60km? How significant is this effort and have others found that this strategy works in a triathlon or not? How much extra effort can a rider 'afford' to put out up the hills, if any? Or should they just hold a higher watts smoothly throughout the ride?

Does anyone have any experience in the area of having to run after a time trial (triathlon) and can they please provide input and experiences and hyposthesis? I have searched various place on the internet and I haven't found many discussions on this subject.

I apologize in advance to any roadies who have wasted their time reading a post with the word triathlon in it :)
(Even L.A. used to race in a Speedo :D
I've done a lot of work on these questions.

As a starting point, have a look at these two threads. One from Slowtwitch where I analysed an Ironman bike file from one rider. The link takes you to page 3 where my analysis really kicks in but you might want to go through it from the beginning:

http://forum.slowtwitch.com/gforum.cgi?do=post_view_flat;post=2066900;page=3;sb=post_latest_reply;so=ASC;mh=25;

The other a wattage forum thread about Optimal TT pacing. This references a paper I wrote on the subject which is available for download on the wattage files page. The paper outlines the methodology, a case study and the results of my analysis on a range of TT efforts from Pros to club riders. You'll need a google groups sign on to view though:

http://forum.slowtwitch.com/gforum.cgi?do=post_view_flat;post=2066900;page=3;sb=post_latest_reply;so=ASC;mh=25;
 
Thanks for all the responses. I am still reading the ST forum posts that Alex suggested. It is good stuff. A lot of reading!! Now I remember why I stopped looking at the ST forum. Hours slip away with the volume of posts there.